Chapter 11, Problem 53SE

In an automated chemical coating process, the speed with which objects on a conveyor belt are passed through a chemical spray (belt speed), the amount of chemical sprayed (spray volume), and the brand of chemical used (brand) are factors that may affect the uniformity of the coating applied. A replicated 23 experiment was conducted in an effort to increase the coating uniformity. In the following table, higher values of the response variable are associated with higher surface uniformity:

Surface
				Uniformity
				Repli-	Repli-
	Spray	Belt		cation	cation
Run	Volume	Speed	Brand	1	2
1	_	_	_	40	36
2	+	—	—	25	28
3	-	+	—	30	32
4	+	+	-	50	48
5	—	_	+	45	43
6	+	—	+	25	30
7	—	+	+	30	29
8	+	+	+	52	49